Temperature compensator for brake adjusters



Feb. 21, 1939. sMlTH 2,147,996

TEMPERATURE COMPENSATOR FOR BRAKE ADJUSTERS Filed June 27, 1958 Ga-one: L. SMITH. w; g

Arm/war Patented Feb. 21, 1939 UNITED STATES PATENT OFFICE TEMPERATURE COMPENSATOR FOR- BRAKE ADJ USTERS Application June 27, 1938, Serial No. 216,097

, 5 Claims.

I show in this application thermostatic means which will not be afiected in its operation by seasonal changes in atmospheric temperature. Such diiference in temperature may vary from in cold climates in winter, to 140 in summer.

Should an operator drive a car from Canada to Florida in the Winter, for instance, the sudden change in temperature would seriously affect the action of any clearance adjusters on his brakes equipped with thermostatic control unless some device were applied to neutralize the effect of large variations in atmospheric temperature, and it is the object of this invention to provide such a device that will render these changes of temperature of no effect upon the adjusting mechanism.

In the drawing shown to illustrate my invention wherein like characters of reference denote corresponding parts in the dilferent views,-

Fig. 1. shows a side elevation of a portion of a brake assembly with most of the brake drum cut away and with my adjuster applied thereto.

Fig. 2 shows a portion of the same View with a modified arrangement of adjuster parts.

Referring to the drawing the numeral i0 represents the brake support plate upon which the brake shoe II is mounted. The lower end of this shoe is pivoted at M to the support plate and upon its flange l2 the brake lining i3 is secured for frictional contact with the brake drum i3b. The usual hydraulic brake cylinder [5 is carried by the plate l0 and has operative connection with the upper end of shoe II by means of the web extension IS. The usual releasev spring for releasing the brake is also shown, all in the well known manner of hydraulic brake construction.

I secure my adjuster box l8 to the plate In by screws or rivets Mia and this box carries the bolt l9 threaded at its left end to the box and carrying an operating wheel 20 at its right end. A torsion spring |9a surrounds the bolt and is connected to the bolt and to the box in such a manner that it will screw the bolt home until stopped by the wheel 20 hitting the end of the box.

Upon the tit |9b on left end of the bolt I9 I pivotally mount a bi-metal strip 2| with its convex side the high-expansion side. To this strip I secure a second bi-metal strip 22 also having its convex side the high-expansion side, and this strip contacts the flange |2 of the shoe II. The two bi-metal strips are spaced apart by heat insulating washers 23 and held together 5 by rivets 24 loosely fitting the holes in strips and washers.

The mechanism operates as follows:

The torsion spring lilo keeps the bolt I 9 lightly screwed up against the strip 2| and thereby forces strip 22 against flange l2. As the shoe is swung out into contact with its drum the adjuster bolt follows up this movement and when the brake is released the spring ll swings the shoe back again by a considerable force against strip 22 thus flexing the strips 2| and 22 and providing the necessary running clearance. When the drum heats up from severe brake application heat is transmitted to the flange i2 and through it by metal to metal contact to the strip 22 and compensation for the expanded drum is efiected in the same manner as described in my application aforesaid No. 181,243. Strip 2|, however, does not heat up as rapidly as its heat is obtained from the air, but 25 its curvature as well as the curvature of 22 will vary with climatic temperatures. This will affect the position of their free ends only, which have nothing to do with the action of the adjuster, as the spacing of strips 2| and 22 at the tit |9b will be substantially the same regardless of the changes in curvature of these strips resulting from changes in atmospheric temperatures.

Thus it is seen that the use of a secondary strip 2| which is largely controlled by atmospheric temperature only, produces a combination which will work in either a cold or hot climate.

Furthermore, strip 2| serves another useful 0 purpose in preventing over-adjustment as the brakes are alternately heated up and cooled 01!. During a severe brake application the temperature rise in the brake drum is rapid, while the other brake parts heat up much more slowly. But when braking action ceases the drum temperature begins to drop while the temperature of the other parts is still rising and will continue to rise until the drum temperature drops to a point of equality with that of the other parts. When this point is reached the temperatures of the drum and the other parts drop together to that of the surrounding air.

Now in controlling the running clearance of the brake the strips 2| and 22 act in much the u of equality with the other brake parts, at which time no adjustment of the brake for drum expansion is necessary. Strip 2| thus becomes not only a compensator for changes in atmospheric temperatures but also for changes in relative temperatures of brake drum with respect to the temperature of the other brake parts.

In Fig. 2 the operation of the parts is the same except that the high expansion sides of the strips 2| and 22 are reversed and the two strips are separated by the length of the adjuster box. Strip 2| is riveted to the end 01 the box it which rests on the plate II but is not bolted to it. The ends oi 2| are secured to plate II by studs 28-28. As a rise of atmospheric temperature tends to increase the pressure of the ends of 22 on the flange |2 this same rise causes the strip 2| to curve so as to move box I. away from the flange l2 and thus ease up this pressure. The dotted lines show to an exaggerated degree, this compensating action for atmospheric temperatures. This arrangement might be found better than that shown in Fig. 1 where the character 0! the brake might cause strip 2| to heat up too rapidly and interfere with the normal action of strip 22 in causing the shoe to follow up the drum expansion due to heat generated by the brake, and thus maintain the running clearance of the brake substantially constant at all times.

I claim:

1. In a brake mechanism, a braking member having brake applying and releasing movements, a stop and thermosensitive means spacing said member from said stop and maintaining said spacing substantially unaffected by changes in atmospheric temperatures.

2. In a brake mechanism, the combination of a braking member, a stop limiting the released position of said member, and thermostatic means included in said stop varying the released position oi said member for variations in the temperature of said mechanism caused by the generation of heat produced by braking action and maintaining said released position substantially unaflected'by variations in atmospheric temperatures.

3. In a brake mechanism, a brake shoe, release mechanism for said shoe, a stop. thermostatic means between said shoe, and said stop varying the released position 01 said shoe for variations in brake temperature caused by the generation or heat produced by brake application and a second thermostatic means maintaining the released position of said shoe substantially invariable for changes in brake temperature caused by atmospheric temperature.

4. In a brake mechanism, a brake drum, a brake shoe for applying a braking action to said drum, an adjuster for said shoe, a first thermostatic element between said shoe and adjuster bending to advance the released position of said shoe towards its drum when the drum temperature rises as a result of brake application, and a second thermostatic element bending to reverse the action of the first element as the drum temperature falls.

5. In a brake mechanism, a brake drum, a brake shoe having brake applying and releasing movements with respect to said drum and an adjuster for said shoe including a thermostatic element bending as its temperature rises to advance the released position of said shoe towards said drum and another thermostatic element bending as its temperature rises to retract said released position.

GEORGE L. SMITH. 

